Prepd by heating bromine with n-caproic acid in the presence of phosphorus trichloride as catalyst: Clarke, Taylor, Org. Synth. 4, 9 (1924). Resoln into optically active forms by means of the strychnine salt: Levene et al., J. Biol. Chem. 75, 352 (1927); Levene, Mardashew, ibid. 117, 707 (1937).